Evaporator defrosting arrangement



Jan. 12, T954 0. s. GRIMSHAW EVAPORATOR DEFROSTING ARRANGEMENT FiledDec. 12, 1951 lhvehtoFz Charles S. GT'imShaW,

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His Attbr-nqg.

Patented Jan. 12, 1954 EVAPORATOR DEFROSTING ARRANGEMENT Charles S.Grimshaw, Erie, Pa., assignor to General Electric Company, a corporationof New York Application December 12, 1951, Serial No. 261,165

13 Claims.

My invention relates to refrigerator evaporators and more particularlyto defrosting arrangement for evaporators.

In many household refrigerators, the evaporator for cooling the foodstorage compartment is exposed to the air within the compartment and isoperated at a temperature below the freezing point of water. As aresult, moisture in the air within the storage compartment condenses onthe evaporator and collects thereon in the form of frost. This layer offrost on the surface of the evaporator has an insulating effect reducingthe efficiency of the evaporator in cooling the food storagecompartment. It is accordingly necessary to remove this frost from timeto time in order to prevent too serious a reduction in the operatingefiiciency of the refrigerating apparatus. In many cases, thisdefrosting is accomplished manually by stopping operation of thecondensing unit and placing trays of warm water on the refrigeratedsurfaces of the evaporator. Defrosting in this manner is a somewhattimeconsuming and disagreeable operation. By my invention a relativelyuniform heating of the evaporator surface is accomplished and defrostingis achieved without the necessity of using trays of warm water and thelike, and the time required for the completion of the operation ismaterially reduced.

Accordingly, it is an object of my invention to provide an improvedarrangement for defrosting a refrigerator evaporator.

It is another object of my invention to provide an improved arrangementfor defrosting a refrigerator evaporator which maintains a substantiallyuniform temperature throughout the entire evaporator during thedefrosting operation.

Further objects and advantages of my invention will become apparent asthe following description proceeds and the features of novelty whichcharacterize my invention will be pointed out with particularity in theclaims annexed to and forming a part of this specification.

In carrying out the objects of my invention, a flooded evaporatorincluding continuous serpentine tubing is employed. Defrosting isaccomplished by circulating vaporized refrigerant through theevaporator. The heating and circulating of the refrigerant is achievedby providing means for supplying heat to the continuous serpentinetubing of the evaporator at two points spaced along the series circuitthereof. In the specific embodiment illustrated, the tubing includes ahorizontal portion and a vertical portion, one of the heating pointsbeing located in the horizontal portion of the evaporator and the otherof the points being located in the vertical portion of the evaporator.

For a better understanding of my invention, reference may be had to theaccompanying drawing in which Fig. 1 is a side elevation view of aportion of a refrigerator incorporating an embodiment of my invention.

Fig. 2 is an isometric view of the evaporator including a schematicwiring diagram, the walls upon which the evaporator tubing is mountedbeing shown in dotted lines for clarity.

Referring to Fig. 1, there is shown a refrigerator cabinet I includingan outer wall 2 and a spaced inner wall or liner 3, the inner wall 3defining a food storage compartment 4. The

access opening of the food storage compartment is closed by a door 5.

In order to cool the food storage compartment 4, an evaporator 6 ismounted in the upper portion of this compartment. In the formillustrated, the evaporator 6 includes a supporting sheet structure orwall structure '1 including a vertical rear wall or sheet 8 and ahorizontal bottom wall or sheet 9. The refrigerating portion of theevaporator includes a header In which is positioneo. near the top of therear vertical sheet or wall 8. The evaporator 6 is of the floodedrecirculating type and includes continuous tubing H arranged inserpentine form and secured to the supporting sheet structure I. One endof the continuous tubing II is connected to the header ill of theevaporator at 2 below the normal level of liquid refrigerant in theheader It. The other end l3 of the continuous tubing II is connected incommunication with the interior of the header I0 above the normal levelof liquid refrigerant in the header. By this arrangement, the liquidrefrigerant flows from the header to the tubing II at the connection [2and vaporiizged refrigerant is discharged into the header at In the formillustrated, the serpentine tubing H includes a first portion [4 whichis arranged in a horizontal plane and secured in any suitable manner, asby brazing or welding, to the exterior or bottom surface of the bottomhorizontal wall 9. Liquid refrigerant is supplied to the horizontalportion 54 through a vertical tubing section i5 extending between theconnection [2 at the header and the horizontal portion I4 of the tubing.A trap I6 is provided at the bottom of the tubing section [5 immediatelypreceding the horizontal portion [4. The vertical tubing section i5 isspaced from the vertical wall or sheet 8 of the evaporator, and hence isnot in heat exchange relationship therewith. The tubing further includesa second portion I? which is arranged in a vertical plane and is securedin any suitable manner, as by brazing or welding, to the exterior prrear surface of the rear vertical wall 8. Liquid refrigerant issuppliedftothe evapora tor from a condensing unit (not shown) through aliquid line or capillary tube l8. lary tube is connected to the tubingil in the first or horizontal portion M thereof near 'the junctionbetween the horizontal portion FE and the second or vertical portion ilvaporized refrigerant from the header is r turned to the condensing unitthrough a suction line it.

The evaporator 8 and thetubing ll thereofare exposed to the air withinthe foods'torage coinpartment 4 during operation of the refrigerator.

In order to maintain a sufficiently low temperature the food storagecompartment 4, and in ord 'mteih'etempereuirewithintheiompart'riintfforinedby the wall structure I siifficiently m orpreservation of lffrozen' fo'o evap- "s'br this"typeare'uermeuy'opereteue a V p at'ure siihstantially below 'f'the freezingpoint of water. As aresult rhoi's'turein'the "air witliin we "foodstorage compartment condenses on.theevaporator"andcollects thereon asfrost, feveiit'iially'forminga manketcr such frost over 'thetubiiig' endwalls'of the evaporator, This rresraerses an insulating medium reducingthe cooling effector the evaporator and reducingthe einjien'ey'eftherefri'gerating system. It is. desirable therefore to'removethis'blank'et of frost from tinie'to time to maintain operation of therefrigeratingsystem at a reasonably high effi- *eien'e'y. In'accordai'ic'e'with' invention, -an 'ar- .rangement is providedwhereby'heat is supplied to the evaporator for vaporizing refrigerantwithin the tubingand' for assisting in circulating the refriger'antthrough the tubing so that the vaporizedref'rigerant asit reco'ndensesgives up'heat t'o' thejtubing for melting the frost therefrom. "Spefically,"lfprovide a defrosting"arrangement Tin which heat is suppliedto thecontinuous tubj'ingiat two points or sections thereof spaced alongjthaseries circuitof the 'continuoustubing. In thef'form illustrated,one of "these sections is located in a horizontal portion of the tubingand the other is located in the vertical portion of the tubing. p 7 a 7p ,7 Thus one heater'2ii is located adiacentasection 2| of ''ahorizontal portion of the tubing l l. The 'heater'20 is located at thebeginning of the hori- "zorital portionof the tubing ii, that is,immediat'elyfollowing the trap it. This heater may beanjelectric'heating element or other suitable heating device forsupplyingheat to the tubing alndito the refrigerant therein. By way of example;this heater may conveniently be the sheathed "insulated type of heatingelement sold'under the shade-mark Calrod. A similar type ofrheater 22isfpositioned in heat exchange relationship'with "a section 123 of thevertical portion of the tubing H... This heater 22 is located near thebottom of this vertical portion ii and the vaporization of liquidrefrigerant within the tubing at this point assists in promoting upwardcirculation of "both vaporized and liquid refrigerant'in theveritic'al'fportion ll. The heater 2% vaporizes refrigerant and,becauseof the circulation induced by ,heater 22, the' refrigerant circulatesthrough the @tubing of the horizontal portion i i and, in recon-"dens'ingjit gives up heat to the tubing; thereby effecting melting offrost therefrom. The heaters This oapil 20 and 22 may be secured in heatexchange relat tionship with the sections 21 and 23 of the tubingrespectively in any suitable manner. By way of example, the heaters maybe held in such heat exchange engagement with the tubing by clamps 24and 25, respectively, The clamp 24 is removably secured tothe bottomsheet 9 of the evaporator wall structure in'any suitable manner, as byscrews (not shown) and the clamp 25 is similarly removably secured tothe rear sheet 8 of this wall structure.

As indicated schematically in Fig. 2, the heaters 20 and 22.are suppliedin series with power from "amysuitablefelectrical power supply throughlines 28, It is desirable that the heaters 20 and 22 be connected-series. Should the two heaters beconnected in parallel and should theheater 22 in thevertical portion 11 burn out, the heater 20 in'th'ehorizontal portion M might merely form a large pocket of vaporizedrefrigerant Without effectivecirculation thereof. Such lack ofcirculation and, hence, lack of replenishment of liquid refrigerant inthe area of the heater 20 might result in damagefrom overheating in thisregion of the evaporator. A switch 2'! is provided-for controlling theenergization of the heaters 20 and i2, the'switch 2'! being adapted inits closedposition to engage contacts 28 to close the circuitto theheaters 213 and'22 in series. The switch 21 may be operated in anysuitablemanner for initiating energization of the heaters; for example,it may be manually closed to initiatethis heating/it may be closed bysome mechanism rm automatically initiating defrosting atpredeterminedintervals; etc.

section2! of the'tubing. Refrigerant normally circulates in thedirection of the arrows shown in Fig.2 because'of the head of liquidrefrigerant imposed on the'tubing'through the connection at 12. Duringdefrbsting'the refrigerant vaporizedby'the heater 2!] in the section 2|circulates in the direction of the arrows moving with it a quantity ofliquid depending upon the head produced by the difference in density oftherefrigerant in the'two vertical sections I5 and" ll of the closedrefrigerant path. 'A circulation rate will be establishedso that theflow losses will be equal to this head. The trap l6 blocks any tendencyof refrigerant vaporized by the heater 20 to rise upwardly through thesection 15 at the tubing and insures 'circulation'of refrigerant in thenormal direction. 'The circulating vaporized refrigerant, inrecondensing, supplies heat to the horizontal portion 'M of the tubing,efiecting melting "of frost'from this horizontahportion. The heater 22on'the vertical portion 17' of the tubing alsoeffects vaporization ofliquid refrigerant in the tubing, specifically at the section 23adjacent the heater, and the rising bubbles of vaporized refrigerant"reduce the head in the vertical 'tubi'ng portion i1, assistingcirculation of downwardly 'from"the* header into the horizontal portionM. The vaporized refrigerant in rising upwardly through the tubingportion l1 recondenses therealong, giving up heat to this portion of thetubing and effecting melting of frost therefrom.

The utilization of the two heaters shown and the disposition of theseheaters, one at the beginning of the horizontal portion and one at thebottom of the vertical portion causes a relatively uniform temperatureto bemaintained throughout the evaporator and allows the utilization ofa tubing of relatively small size since the vaporized refrigerant needflow only a substantially shorter distance than would be the case werethe defrosting attempted with a single heater. It also provides foreffective defrosting of a horizontal sheet which is more acceptable thana sloping sheet for the bottom of an evaporator.

The significance of the flooded recirculating evaporator in thedefrosting operation should be noted. In cases where a series system isemployed, that is where the capillary tube is connected at one end ofthe evaporator tubing and the header at the other, it is'possible forthe heater to blow the tubing dry. Under these circumstances, continuedapplication of heat by the heater could burn out the heater or cause damage to the evaporator through local overheating. By my arrangementemploying a flooded recirculating evaporator where both ends of theevaporator tubing are connected to the header, a supply of liquidrefrigerant to the tubing in the region of the heater is assured, andthe possibility of the evaporator being blown dry, with resultantdamage, is minimized.

While I have shown and described a specific embodiment of my invention,I do not desire my invention to be limited to the particularconstruction shown and described, and I intend, by the appended claims,to cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A flooded evaporator comprising a header and a single continuouslength of tubingconnected at both ends to said header and providing aseries circuit for refrigerant, said tubing including a first portionand a second portion in series circuit with said first portion, one endof said tubing being connected to said header below the level of liquidrefrigerant therein for supplying liquid refrigerant to said firstportion, the other end of said tubing being connected to said headerabove the level of liquid refrigerant therein for conducting vaporizedrefrigerant from said second portion to said header, and means forsupplying heat to said evaporator at two sections of said tubing spacedalong the series circuit thereof for defrosting said evaporator, heatsupplied to at least one of said sections being also effective forinducing circulation of refrigerant through said continuous tubing.

2. A flooded evaporator comprising a header and continuous tubingconnected at both ends to said header, said tubing including a firstportion arranged in a horizontal plane and a second portion in seriescircuit with said first portion and arranged in a vertical plane, oneend of said tubing being connected to said header below the level ofliquid refrigerant therein for supplying liquid refrigerant to saidfirst portion, the other end of said tubing being connected to saidheader above the level of liquid refrigerant therein for conductingvaporized refrigerant from said second portionto said header, and meansfor supplying heat to said evaporator at two sections of said tubing fordefrosting said evaporator, one of said sections being located in thehorizontal portion of said tubing whereby heat is supplied to liquidrefrigerant in said tubing at said one of said sections to vaporize saidrefrigerant for defrosting said horizontal portion, the other of saidsections being located in the vertical portion of said tubing wherebyheat is applied to liquid refrigerant in said tubing at said other ofsaid sections to vaporize said refrigerant for defrosting said verticalportion and for inducing circulation of refrigerant in said tubing.

3. A flooded evaporator comprising a header and continuous tubingconnected at both ends to said header, said tubing including a firstportion arranged in a horizontal plane and a second portion in serieswith said first portion and arranged in a vertical plane, one end ofsaid tubing being connected to said header below the level of liquidrefrigerant therein for supplying liquid refrigerant to said said firstportion, the other end of said tubing being connected to said headerabove the level of liquid refrigerant therein for conducting vaporizedrefrigerant from said second portion to said header, and means forsupplying heat to said evaporator at two sections of said tubing spacedalong the series circuit thereof for defrosting said evaporator, one ofsaid sections being located near the beginning of said horizontalportion for vaporizing liquid refrigerant to defrost said horizontalportion, the other of said sections being located at the bottom of saidvertical portion for vaporizing liquid refrigerant to defrost saidvertical portion and to induce circulation of refrigerant through saidcontinuous tubing.

4. A flooded evaporator comprising a header and continuous tubingincluding a first portion arranged in a horizontal plane and a secondportion in series with said first portion and arranged in a verticalplane, one end of said tubing being connected to said header below thelevel of liquid refrigerant therein for supplying liquid refrigerant tosaid horizontal portion, the other end of said tubing being connectedtosaid header above the level of liquid refrigerant therein for conductingvaporized refrigerant to said header, and means for supplying heat tosaid evaporator at two sections of said tubing for defrosting saidevaporator, one of said sections being located near the point whereliquid refrigerant reaches said horizontal portion from said header, theother of said sections being located near the bote tom of said verticalportion of said tubing.

5. A flooded evaporator comprising a header and continuous tubingincluding a first portion arranged in a horizontal plane and a secondportion in series with said first portion and arranged in a verticalplane, said tubing including a vertical section connected to said headerbelow the level of liquid refrigerant in said header for supplyingliquid refrigerant to said horizontal portion, said tubing being formedto provide a trap between said vertical section and said horizontalportion, the other end of said tubing being connected to said headerabove the level of liquid refrigerant therein for conducting vaporizedrefrigerant to said header, and means for supply ing heat to saidevaporator at two sections of said tubing for defrosting saidevaporator, one of said sections being located in said horizontalportion immediately following said trap, the other of said sectionsbeing located near the bottom of said gr qa .pqr mois d u ms.-.

ii. A refrigerating system including a condense ing unit and a floodedevaporator, said evaporator comprising a header and continuous tubingincluding a first portion arranged in a horizontal plane and a secondportion in series with said first portion and arranged ina verticalplane, one end of said tubing being connected to said header below thelevel of liquid refrigerant for supplying liquid refrigerant to saidhorizontal portion, the other end of said tubing being connected to saidheader above the level of liquid refrigerant therein for conductingvaporized refrigerant to said header, and means for supplying heat tosaid evaporator at two sections of said tubing for defrosting saidevaporator, one of said sections being located near the point whereliquid refrigerant reaches said horizontal portion from said header, theother of said sections being located near the bottom of said verticalportion of said tubing, and a conduit for supplying liquid refrigerantto said evaporator from said condensing unit to said evaporator, saidconduit being connected to said horizontal portion of said tubing at apoint immediately preceding said vertical portion.

'7. In combination with a flooded evaporator comprising a header and asingle continuous length of tubing connected at both ends to said headerand providing a series circuit for refrigerant, said tubing including afirst portion and a second portionin series with said first portion, oneend of said tubing being connected to said header below the level ofliquid refrigerant therein for supplying liquid refrigerant to saidfirst portion, the other end of said tubing being connected to saidheader above the level of liquid refrigerant therein for conductingvaporized refrigerant to said header, a defrosting arrangement for saidevaporator comprising a first heater disposed in heat exchangerelationship with a section of said first portion of said tubing forsupplying heat to liquid refrigerant therein to vaporize saidrefrigerant for defrosting said first portion, and a second heaterdisposed in heat exchange relationship with a section of said secondportion of said tubing for supplying heat to liquid refrigerant thereinto vaporize said refrigerant for defrosting said second portion, saidsecond heater also being eifective for inducing circulation ofrefrigerant through said continuous tubing;

8. A refrigerating system including a flooded evaporator, saidevaporator comprising a header and continuous tubing including a firstportion arranged-in a horizontal plane and a second portion in serieswith said first portion and arranged in a vertical plane, one end ofsaid tubing being connected to said header below the level of liquidrefrigerant therein for supplying liquid refrigerant to said horizontalportion, the other end of said tubing being connected to saidheaderabove the level of liquid refrigerant therein for conducting vaporizedrefrigerant to said'header, a first heater for supplying heat to saidhorizontal portion for vaporizing liquid-refrigerant-to effectdefrosting of said horizontal portion, said first heater being disposedin heat exchange-relationship with a section of said horizontal portionlocated substantially in the region where liquid refrigerant reachessaidhorizontal portion from said header, and a second heater forsupplying heat to said vertical portion for effecting vaporization ofliquid refrigerant to eiiect defrosting of said vertical portion and toinduce circulation of refrigerantthrough said tubing,

8 said second heater being disposed in heat exchange relationship with asection of said vertical portion located near the bottom of saidvertical portion.

9. A refrigerating system including a flooded evaporator, saidevaporator comprising a header and continuous tubing including a firstportion arranged in a horizontal plane and a second portion in serieswith said first portion and arranged in a vertical plane, said tubingincluding a vertical section connected to said header below the level ofliquid refrigerant in said header for supplying liquid refrigerant tosaid horizontal portion, said tubing being formed to provide a trapbetween said vertical section and said horizontal portion, the other endof said tubing being connected to said header above the level of liquidrefrigerant therein for conducting vaporized refrigerant to said header,a first heater for supplying heat to said horizontal portion forvaporizing liquid refrigerant to effect defrosting of said horizontalportion, said first heater being disposed in heat exchange relationshipwith a section of said horizontal portion located immediately followingsaid trap, and a second heater for supplying heat to said verticalportion for eiiecting vaporization of liquid refrigerant to effectdefrosting of said vertical portion and to induce circulation ofrefrigerant through said tubing, said second heater being disposed inheat exchange relationship with a section of said vertical portionlocated near the bottom of said vertical portion.

19. A refrigerating system including a flooded evaporator, saidevaporator comprising a header and continuous tubing including a firstportion arranged in a horizontal plane and a second portion in serieswith said first portion and arranged in a vertical plane, one end ofsaid tubing being connected to said header below the level of liquidrefrigerant therein for supplying liquid refri erant to said horizontalportion, the other end of said tubing being connected to said headerabove the level of liquid refrigerant therein for conducting vaporizedrefrigerant to said header, a first heater for supplying heat to saidhorizontal portion for vaporizing liquid refrigerant to efiectdefrosting of said horizontal portion, said first heater being disposedin heat exchange relationship with a section of said horizontal portionlocated substantially in the region where liquid refrigerant reachessaid horizontal portion from said header, and a second heater forsupplying heat to said vertical portion for effecting vaporization ofliquid refrigerant to effect defrosting of said vertical portion and toinduce circulation of refrigerant through said tubing, said secondheater being disposed in heat exchange relationship with a section ofsaid vertical portion located near the bottom of said vertical portion,said first heater and said second heater being connected in a serieselectrical circuit to insure simultaneous energization anddeenergizationof said heaters.

11. A refrigerating system including a flooded evaporator, saidevaporator comprising a header and continuous tubing including a firstportion arranged in a horizontal plane and a second portion-m serieswith said first portion and arranged in'a vertical-plane, one end ofsaid tubing being connected to said header below the level of liquidrefrigerant therein for supplying liquid refrigerant to said horizontalportion, the other end ofsaidtubing being connected to said headerabove" the level ofliquid refrigerant therein 1 for zontal sheet and avertical sheet and continuous 45 2276454 Becker 1942 conductingvaporized refrigerant to said header. tubing including a horizontalportion secured to a first heater for supplying heat to said horizontalsaid horizontal sheet and a vertical portion in portion for effectingvaporization of liquid refrig- H said tubing, a second clamp for holdingsaid secfrigerant to said header, a first heater for supond heateragainst a section of said vertical porplying heat to said horizontalportion for vaportion located near the bottom of said vertical l5 izingliquid refrigerant to eifect defrosting of portion. said horizontalportion, said first heater being 12. In combination with an evaporatorincluddisposed adjacent a section of said horizontal continuous tubingincluding horizontal and verliquid refrigerant reaches said horizontalportical portions secured to said horizontal and ver- 20 tion from saidheader, a first clamp secured to tical sheets respectively and a headerat the upsaid horizontal sheet for holding said first heater per portionof said vertical sheet having both in heat exchange relationship withsaid section ends of the serpentine tubing connected thereof saidhorizontal portion of said tubing for vawith a section of saidhorizontal portion of tubduce circulation of refrigerant through saidtubing for supplying heat to liquid refrigerant therein for vaporizingsaid refrigerant to defrost said 35 CHARLES S. GRIMSHAW.

horizontal sheet, and a second heater disposed in heat exchangerelationship with a section of References cued m the file of thls patentsaid vertical portion of tubing for supplying heat UNITED STATES PATENTSto liquid refrigerant therein for vaporizing said refrigerant to defrostsaid vertical sheet and to 40 ggia i ff Aug 32 circulation ofrefrigerant through said 29241612 sulzberger 17, 1935. 13. Arefrigerating system including a flooded 5333 333 2335 3? evaporator,said evaporator comprisinga hori-

